The present invention relates to separating barriers or insulator pads used with mattresses and upholstered furniture with spring support, including cushions and chair seats installed in motor vehicles and airplanes, and methods for making such barriers or pads.
Spring support systems, such as coil springs provided in mattresses and chair seats, usually are separated from the cushioning material or top furniture or mattress surface. The separating barrier or insulator performs several functions. First, it protects the cushion from the sharp tips of the wire springs. Without a separating barrier or insulator, the edges of the wire springs could puncture the cushioning material, damaging the cushion and in time possibly protruding from the surface of the cushion to poke or scratch the individual who sits or reclines upon the cushion. Second, it forms a bridge between the individual springs so that the load on the cushion is more evenly distributed across the springs. Without a separating barrier or insulator, the coil springs would act upon the cushioning material individually, eventually making the surface of the cushion feel bumpy and uncomfortable to the individual who sits or reclines upon the cushion (sometimes called xe2x80x9ctelegraphingxe2x80x9d). Third, it adds some cushioning, albeit to a lesser degree when compared to the furniture cushion that is placed on top of the insulator pad.
At present, separating barriers or insulator pads are placed between the tops of the springs and the cushions or mattress pad tops. Such barriers or pads are usually formed from an inexpensive fibrous pad material, such as xe2x80x9cshoddy,xe2x80x9d a layered sheet material composed primarily of textile scraps that are needle-punched, or, in some cases, compressed together with resin or glue. Shoddy is manufactured by a number of companies, including Jamesville Products Company and Chris Craft Company. Resinated shoddies that have increased stiffness and resist bending are often selected for insulator pads.
Using shoddies or resinated shoddies for the barrier or insulator pads has significant disadvantages. Because shoddy is formed from textile scraps, the product characteristics vary from lot to lot. The weight and thickness of the sheet of shoddy may vary even within the same lot. Such product variations cause significant performance variations. Moreover, the resins used to form the shoddy will break down or deteriorate and lose stiffness overtime. After only a short time in use, the shoddy will begin to compress its thickness, reduce its stiffness and lose its insulating properties. If the insulating pad breaks down, the cushion will have an uncomfortable, lumpy feel because the load atop the cushion is not evenly distributed over the springs.
U.S. Pat. No. 3,923,293 issued Dec. 2, 1975 to Wiegand discloses a spring insulator for mattresses comprising a one-sixteenth to one inch thick sheet of extruded polyethylene plastic foam sheet. Wiegand selects polyethylene over polyurethane because polyethylene has the strength and structural rigidity required. According to Wiegand, the stiff polyethylene foam sheet alone may form the insulator. Optionally, the polyethylene foam sheet may be bound to the wire springs of the mattress structure, or alternatively to the padding material forming the mattress pad (which may be cotton batting, polyurethane foam, or the like). A cotton or plastic net may be attached to the polyethylene sheet to reinforce the sheet and prevent creeping (i.e., shifting movement) within the spring cushion assembly. In view of the inherent stiffness of the polyethylene sheet, the net need not impart stiffness to the sheet. The Wiegand spring insulator requires added sound-dampening because the polyethylene sheet used is stiff enough to act as a drum head when the sheet lifts off and recontacts the mattress springs.
An object of the present invention is to provide a barrier or insulator pad that has substantially uniform physical properties, with good isolation characteristics, load distribution capabilities and offers some degree of cushioning, without the drawbacks associated with the prior art.